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Discussion Starter · #1 ·
Took the 1998 Formula Z 670 out for a final rip yesterday. Here's what happened.

Starts fine on first pull. Idles perfectly. Runs well. No issues with throttle. 135psi on each cylinder.

When 3/4 throttle, it runs around 6000rpm's (according to gauge). At full throttle it revs up to 7100-7200 rpms then throttles back down. Top speed is only 60mph. I have done much more than this speed on this sled earlier in the year and saw rpms stay at around 7900 at WOT.

What gives? What could be the likely cause? Clutch cleaning needed? Carb cleaning?
 

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Is there enough fuel pumped to the carbs, or the RAVE valves opening, or are the clutches limiting the top speed?
 

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Using a crayon draw a line from the outside edge of the inner clutch down about 1". Take the sled for a run and check the crayon mark. The crayon should wiped off up to 1/8" to 1/4" down from the outer edge of the clutch face. If it's not your clutch isn't working properly and will need servicing. If the secondary clutch isn't opening up as it should it may be holding the clutch in a low ratio. The inner half (movable half) should rotate and move to open and let the belt go lower in the secondary. If the inner half is seized the secondary won't open and change the gear ratio into high gear.

Lynn
 
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A 670 should be turning around 8100 rpms.
 

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is the parking brake stuck?
 

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Discussion Starter · #9 ·
Brakes are good. I pulled caliper, cleaned brake pistons, cleaned reservoir, and replaced fluid. Brakes should be good.

I'm going to go back and inspect/clean carbs and exhaust valves (i've never taken the exhaust valves apart). I'll inspect the drive belt.

I'm guessing here, but I think the RPM reduction is in the clutches (maybe both primary and secondary). I've owned the sled for 3 years, and I don't believe the clutches have ever been serviced.
 

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Brakes are good. I pulled caliper, cleaned brake pistons, cleaned reservoir, and replaced fluid. Brakes should be good.

I'm going to go back and inspect/clean carbs and exhaust valves (i've never taken the exhaust valves apart). I'll inspect the drive belt.

I'm guessing here, but I think the RPM reduction is in the clutches (maybe both primary and secondary). I've owned the sled for 3 years, and I don't believe the clutches have ever been serviced.
Get a new spring for each of the clutches and make sure to set the secondary to the rite poundage with a fish scale. Had similar problems with my 2000 700 summit did new springs and set secondary the the rite pounds and it woke up like crazy brand new sled.

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